Thanks for the link, I will have to give it a read. I have not decided on a diffuser yet, I actually design oil reservoirs as part of my job, the main difference between work and splitters is a small reservoir for us is 80 gallons, splitters we are only talking 5 to 25 gallons depending on peoples pump. Oil retention time is something I deal with everyday as well but our oil systems are doing completely different things so having 3,5, or 8 minutes worth of oil for a 16/4 gpm pump that the OP is using is overkill and cost prohibitive. Info on total gallons for log splitters in reference to the GPM of the pump is a little "seat of the pants" from things I have read so that makes me lean closer to 3 minutes worth of oil at the high pressure side. OP's case that would be a 12 gallon reservoir, and that 12 gallons is actual max operating level and not when the res. is completely full. you need room for heat expansion and air. I think often times the oil reservoir does not get the attention it deserves during a splitter build so I am glad to see the OP asking questions and trying to get it right. Sure there are a million ways to skin a cat, but some are better than others. Plus why spend more money on steel for extra baffles if they are not needed, heck a lot of splitters on the market do not even have a baffle.